1. Field of the Invention
The present invention relates to a plasma display panel drive apparatus and to a drive method therefor, and more particularly to a plasma display panel drive apparatus with improved display quality and a drive method therefor.
2. Related Art
In a plasma display panel, a charge recovery circuit is provided to improve the power efficiency.
A basic approach to charge recovery by the charge recovery circuit is that which focuses on the functioning of an AC-type plasma display as a capacitor after the completion of discharge, wherein the electrical charge accumulated on the panel is extracted using an LC resonant circuit, this being used when discharging again, thereby reducing the reactive power and improving the power efficiency.
However, if the time constant of the LC resonant circuit is made large in order to achieve a sufficient recovery efficiency, the action of electrical charge recovery causes a loss of sharpness in the sustaining pulse applied to the scanning and common electrodes, so that there is a tendency for discharge to start before the drive voltage has risen completely. If discharge occurs midway during electrical charge recovery, the discharge current is supplied from the LC resonant circuit rather than the power supply line, the energy stored in the inductance being the only source of supply, so that the power supply capacity is small, making the voltage drop due to the discharge current large. Because of this voltage drop, the discharge is weakened, resulting in a reduced intensity.
A strong discharge can be caused in order to increase the intensity. It is also effective to make the rising edge and the falling edge of the drive waveform sharp, and this can be achieved by advancing the timing after the charge recovery at which the electrode potential is fixed at the power supply potential. If this is done, however, there is not only a decrease in the charge recovery efficiency, but there is an increase in the variation in intensity (hereinafter referred to as the load variation) caused by a variation in the display load amount, which is established by the number of light-emitting pixels in one line.
However, in order to reduce the variation in the intensity and obtain smooth gray-scale characteristics, it is preferable to retard the timing of fixing the electrode potential to the power supply potential, and it is difficult to achieve these conflicting conditions.
Accordingly, in order to improve on the above-noted drawbacks in the prior art, it is an object of the present invention to provide a novel plasma display panel drive apparatus and drive method therefor, wherein when the overall screen display intensity is high and an image is displayed that requires smooth gray-scale rendering, the clamp timing of the sustaining pulse is controlled so as to give priority to gray-scale characteristics, and when the overall screen display intensity is low and a high peak intensity is required, the clamp timing of the sustaining pulse is performed so as to achieve a high peak intensity, thereby improving the display quality.